WebSocket, Socket.IO, SSE & GraphQL Tester

Connect, send and inspect real-time traffic. Your browser talks straight to your server — no proxy, no sign-up, nothing stored on ours.

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Help shape WebSocket, Socket.IO, SSE & GraphQL Tester

The bug you just noticed will fade in 3 minutes. The feature idea will vanish after your next tab switch. Crazy peps don't suffer silently.

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Frequently Asked Questions

No. Your browser connects directly to the server you enter — no proxy in between. Tabs, saved messages and variables are stored only in this browser's local storage, and share links strip tokens and passwords.

Raw WebSocket (text, JSON and binary), Socket.IO v2, v3 and v4 with namespaces and acks, Server-Sent Events over fetch, and GraphQL subscriptions over both graphql-transport-ws and the legacy Apollo subscriptions-transport-ws protocol.

Browsers don't allow custom headers on the WebSocket handshake. Pass tokens as a query parameter, a subprotocol, a cookie, the Socket.IO auth payload, or an auth message sent automatically on connect. SSE and Socket.IO polling do support headers here.

No. Sockets run in a background worker, the log is virtualized, and a bounded buffer drops the oldest messages when full. We tested 20,000 messages per second with the page staying responsive. Export first if you need everything.

Browsers hide the real reason on purpose. Usually the server is down, the host, port or path is wrong, TLS failed, or a proxy blocks upgrades. The tool lists likely causes for your setup and offers one-click fixes like switching Socket.IO version.